This is an amended proposal for a 5-year continuation of a longitudinal study that has assessed, since birth, fluoride exposures in a cohort of Iowa children. In this study, assessment of dietary and non-dietary fluoride exposures will continue at four month intervals for children in the birth cohort (currently aged 26-60 months). Parents will provide detailed data on their children's fluoride exposures and ingestion using written questionnaires and 3-day dietary diaries. Composite indexes of fluoride exposures and ingestion will be reported, both by source and in total. Total dietary fluoride, non-dietary fluoride, and combined dietary and non-dietary fluoride intake will be estimated at each age. Dental fluorosis and caries prevalence and severity in the primary dentition will be assessed at age four. Multivariate analyses will determine the relationships between the prevalence and severity of primary tooth fluorosis and caries, and the various fluoride exposures and estimated levels of fluoride ingestion. Similarly, fluorosis and caries prevalence and severity in the early-erupting permanent teeth will be assessed for the children reaching age 7-8 during the study period, and relationships among primary and permanent tooth dental fluorosis and caries will be assessed. Assessment of the strength of the associations between these permanent tooth disease outcomes and the prospectively-collected data on fluoride exposures will be initiated, with continuation in a subsequent grant period. The results will build on the data already collected longitudinally on fluoride exposures/ingestion and are expected to increase our understanding about the delicate balance between caries prevention and dental fluorosis in assessing the optimal use of fluorides. The ultimate goal will be to provide the scientific basis necessary to assure that fluorides can be used appropriately for maximum public health caries prevention with minimal dental fluorosis risk.